Gas phase generation and cyclisation reactions of some o-substituted phenyl radicals

Article abstract of DOI:10.1016/S0040-4020(01)90385-0

Flash vacuum pyrolysis of the allyl esters 2 (X=O, S, CH₂, CO) at 900°C (10^-2 Torr) gives dibenzofurans, dibenzothiophenes, fluorenes, and fluorenones respectively as the major products. The mechanism involves the phenyl radical intermediates 1 which equilibrate by intramolecular hydrogen transfer via six-membered transition states, prior to cyclisation.